170 On some Reactions of the Salts of Lime and Magnesia, 
Art. XIX.—On some Reactions of the Salis of Lime and Magne- 
sia, and on the Formation of Gypsums and Magnesian Rocks ; 
by T. Srerry Hunt, F.B.S., of the Geol. Survey of Canada.* 
THE importance, in a geological point of view, of gypsum and 
of the carbonates of lime and magnesia in the forms of limestone, 
dolomite and magnesite, has led me to make a series of re- 
searches, whose results serve to explain many things hitherto 
obscure in the history of these substances. I propose in the 
present paper to describe, in the first place, certain chemical re- 
actions of the salts of lime and magnesia; and, secondly, to con- 
sider the principal facts in the history of gypsums, and magnesian 
rocks, and the theory of their formation, 
lL 
On the action of solutions of bicarbonate of soda on salts of lime 
and magnesia, 
1. In studying some years since the geological relations of alka- 
line mineral waters I found that by the action of a solution of 
carbonate of soda, a partial separation of the salts of lime from 
magnesia could be effected. Subsequent experiments, made with 
dilute solutions of bicarbonate of soda, have led me to the follow- 
ing results. 
If to a solution containing besides common salt the chlorids 
of calcium and magnesium in the proportion of one equivalent 
of each, we add a solution of bicarbonate of soda in water satu- 
rated with carbonic acid, there separates a gelatinous precipitate, 
which very soon becomes crystalline. Collected and ‘washed 
to equal 2°20, 2°00, and 1:23 per cent. The proportion of sepa- 
cies L i" oe salts 
r nated in the solution, which now gave no further preci- 
itate with bicarbonate of soda, but yielded by evaporation to 
; , 2 granular residue of hydrated carbonate of 
with very little lime. In this way, a litre of the solution gave 
"19 grams of carbonate of magnesia, (MgO, CO:) and only 0°14 
grm. of carbonate of lime, while the soluble portion still retai 
in the form of chlorid, 1-176 grms. of magnesia, but no lime. 
* The — — oe —— this paper, or ecg neg 
‘sec aye appeared i rt S ; Canada > 
the others of this section, together with dues of the th se scomni 
fir May. toen weiee, ean ar th \shaloal 6 section 
aay, y . 8) e 0 in 
ready teen published in the Baport of the Surrey but are fow for the first 
